Master replicas require a unique replica identifier that is a 16-bit integer between 1 and 65534. Consumer and hub replicas all have the replica ID of 65535. The replica ID identifies the replica on which changes are made.
If multiple suffixes are configured on one master, you can use the same replica ID for each suffix on the master. In this way, when a change is made on that replica ID, it is possible to identify the server on which change was made.